When an elevator car is caused to be stalled between floors of a building, the persons trapped in the car should remain in the stalled car until trained assistance arrives to facilitate evacuation. However, oftentimes in such situations, some of the trapped persons may attempt to force the elevator door open in an effort to evacuate. In certain instances the above situation can be extremely dangerous, such as, for example, when the stalled elevator is not at or close to a landing. In such a situation, trapped persons may attempt to jump from the elevator car or climb to a landing. As a result, the trapped persons may fall into the hoistway or elevator shaft, resulting in injury.
Such accidents may be avoided by a door restrictor system that is effective to prevent the opening of the elevator car from inside of the car if the car is at a location away from a landing at a floor of the building.
Restrictor systems of the type referred to above generally include a latching or locking member that is typically not accessible from the inside of the elevator car and must be retracted to render the elevator doors operative. These systems may include sensing means which are capable of producing a signal when the elevator car is at or close to a landing and an electrical actuator which retracts the latching or locking member in response to the produced signal.
The floor sensing means may be an electric switch mounted on the elevator car and actuated by contact with contacting members mounted in the elevator hoistway and more specifically, may be typically mounted on the elevator guide rail and located along the path of travel of the switch. These types of switches tend to deteriorate from wear and are prone to breakage causing continual inspection and frequent replacement.
In recent years door restrictor systems have included photoelectric sensors for detecting the location of an elevator car in respect of the floor landings in a building. An infrared light emitter and appropriate detector are carried by the car and are directed towards the elevator guide rail of the wall of the hoistway. Spaced apart infrared reflecting members on the guide rail or hoistway wall are disposed to reflect infrared radiation from the emitting member when the elevator car is at or close to a landing. Similar systems have employed optical sensors and magnetic sensors to sense the floor landing and lock, or in certain instances, unlock the elevator doors by means of an associated solenoid.
These systems have been deemed unacceptable because they default to a certain position when the electrical power is off and associated back-up battery dies.
Accordingly, some manufacturers have adapted a restrictor system which defaults to a locked state and others default to an unlocked state. Each of these systems results in a state that will be wrong in some instances.
It would be desirable to produce a bi-stable locking system which can remain in either the locked or unlocked state when electrical power is terminated.